The first satellite, pictured above, in the U.S. Air Force's GPS 3 program recently passed its thermal vacuum test. Credit: Lockheed Martin.

WASHINGTON – The long-delayed first satellite in the U.S. Air Force’s next generation of positioning, navigation and timing satellites has passed a key test, a top Lockheed Martin executive said Jan. 13.

Rick Ambrose, executive vice president of Lockheed Martin Space Systems of Denver, tweeted that the first GPS 3 satellite has “successfully completed” its thermal vacuum test.

In an email to SpaceNews, Chip Eschenfelder, a Lockheed Martin spokesman, said the thermal vacuum test “is the most comprehensive and perceptive test performed at the spacecraft level.” The test is used to validate that the satellite can operate in extreme temperatures comparable to the space environment, Eschenfelder said.

Lockheed Martin Space Systems is the prime contractor on the GPS 3 program and is under contract to build eight next-generation satellites. The contract includes options for up to four more satellites, and the Air Force has told Congress it expects to execute options for at least two of those satellites.

The Air Force also is in the early stages of a competition for the next batch of satellites beginning with the 11th space vehicle.

The first GPS 3 satellite now is slated to launch no earlier than 2017.

In an April 2015 report, the Government Accountability Office cited a 28-month delay in the launch of the first satellite due largely to trouble developing the navigation payload built by Exelis.

Mike Gruss covers military space issues, including the U.S. Air Force and Missile Defense Agency, for SpaceNews. He is a graduate of Miami University in Oxford, Ohio.